The conventional steam engine is an example of the prior art relative to this invention which will be described in detail hereinafter. If the input pressure with respect to the condenser is beyond design pressure one exhausts from the engine to the condenser too early, thus losing engine power and efficiency by exhausting vapor to the condenser that is at a usable pressure. If, on the other hand, the pressure is below the design pressure, then the pressure of the expanded gas goes to a pressure or vacuum to thus cause a reverse force on a piston with a loss of engine power and efficiency. Thus, in operation, in a steam engine, the design pressure ratio must be maintained to maintain suitable efficiency.
Since water is used for the vapor in a conventional steam engine, it requires a relatively large amount of heat for producing a mole of vapor. This reduces the thermal efficiency of the engine. In addition, water vapor being at a lower pressure at a given temperature than in the case of a refrigerant vapor as used in the present invention, and thus, requires a much larger piston displacement of volume, thus requiring a larger engine for the same power delivered. In that the working temperature of water is much higher than that of refrigerants, a much higher boiler temperature must be maintained to get suitable power output.
Turbines, because of critical design limitations relative to for instance pressure ratios, are expensive to manufacture.
Accordingly, there exists a need to provide a vapor powered engine which can operate from low grade heat energy efficiently without the many critical design limitations as hereinbefore mentioned.